From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug alb_break_llc() decides whether to break LLC preference during active load balance. It does so by testing that every runnable fair task on the source rq prefers its LLC: env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable But the two counters cover different sets. nr_pref_llc_running is updated in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued, so it follows queued tasks. h_nr_runnable is updated in set_delayed()/ clear_delayed() and drops delay-dequeued tasks. So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks, alb_break_llc() returns false, and active balance is free to pull a task off its preferred LLC. Active balance only moves runnable tasks, and this is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB skips the per-task test in can_migrate_task(). The runnable set is the one we want. Fix it on the counter side. A task should be counted in nr_pref_llc_running exactly while it is both queued on its preferred LLC (pref_llc_queued) and runnable (!sched_delayed). Define that membership once in task_pref_llc_runnable(), and adjust the counter only through pref_llc_running_inc()/pref_llc_running_dec() from the four sites that change either input: account_llc_enqueue(), account_llc_dequeue(), set_delayed() and clear_delayed(). Gating every update on the same predicate keeps the delay, wake and dequeue paths from double-counting or underflowing; see the comments at those sites for the ordering. nr_llc_running and sd->llc_counts are not touched and stay on queued semantics. Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC") Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/ Reported-by: Zhan Xusheng Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- crypto/crypto_null.c | 124 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 124 insertions(+) create mode 100644 crypto/crypto_null.c (limited to 'crypto/crypto_null.c') diff --git a/crypto/crypto_null.c b/crypto/crypto_null.c new file mode 100644 index 000000000..fea151df1 --- /dev/null +++ b/crypto/crypto_null.c @@ -0,0 +1,124 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Cryptographic API. + * + * Null algorithms, aka Much Ado About Nothing. + * + * These are needed for IPsec, and may be useful in general for + * testing & debugging. + * + * The null cipher is compliant with RFC2410. + * + * Copyright (c) 2002 James Morris + */ + +#include +#include +#include +#include +#include +#include +#include + +static int null_init(struct shash_desc *desc) +{ + return 0; +} + +static int null_update(struct shash_desc *desc, const u8 *data, + unsigned int len) +{ + return 0; +} + +static int null_final(struct shash_desc *desc, u8 *out) +{ + return 0; +} + +static int null_digest(struct shash_desc *desc, const u8 *data, + unsigned int len, u8 *out) +{ + return 0; +} + +static int null_hash_setkey(struct crypto_shash *tfm, const u8 *key, + unsigned int keylen) +{ return 0; } + +static int null_skcipher_setkey(struct crypto_skcipher *tfm, const u8 *key, + unsigned int keylen) +{ return 0; } + +static int null_skcipher_crypt(struct skcipher_request *req) +{ + if (req->src != req->dst) + memcpy_sglist(req->dst, req->src, req->cryptlen); + return 0; +} + +static struct shash_alg digest_null = { + .digestsize = NULL_DIGEST_SIZE, + .setkey = null_hash_setkey, + .init = null_init, + .update = null_update, + .finup = null_digest, + .digest = null_digest, + .final = null_final, + .base = { + .cra_name = "digest_null", + .cra_driver_name = "digest_null-generic", + .cra_blocksize = NULL_BLOCK_SIZE, + .cra_module = THIS_MODULE, + } +}; + +static struct skcipher_alg skcipher_null = { + .base.cra_name = "ecb(cipher_null)", + .base.cra_driver_name = "ecb-cipher_null", + .base.cra_priority = 100, + .base.cra_blocksize = NULL_BLOCK_SIZE, + .base.cra_ctxsize = 0, + .base.cra_module = THIS_MODULE, + .min_keysize = NULL_KEY_SIZE, + .max_keysize = NULL_KEY_SIZE, + .ivsize = NULL_IV_SIZE, + .setkey = null_skcipher_setkey, + .encrypt = null_skcipher_crypt, + .decrypt = null_skcipher_crypt, +}; + +MODULE_ALIAS_CRYPTO("digest_null"); +MODULE_ALIAS_CRYPTO("ecb(cipher_null)"); + +static int __init crypto_null_mod_init(void) +{ + int ret = 0; + + ret = crypto_register_shash(&digest_null); + if (ret < 0) + goto out; + + ret = crypto_register_skcipher(&skcipher_null); + if (ret < 0) + goto out_unregister_shash; + + return 0; + +out_unregister_shash: + crypto_unregister_shash(&digest_null); +out: + return ret; +} + +static void __exit crypto_null_mod_fini(void) +{ + crypto_unregister_shash(&digest_null); + crypto_unregister_skcipher(&skcipher_null); +} + +module_init(crypto_null_mod_init); +module_exit(crypto_null_mod_fini); + +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Null Cryptographic Algorithms"); -- cgit v1.3.1